STRUCTURAL-CHANGES INDUCED BY ELECTRON-TRANSFER REACTIONS - ISOMERIZATION OF AN ALKYLIDENE MOIETY BY REVERSIBLE METAL-CARBON BOND-CLEAVAGE IN AN ALKYLIDENE-BRIDGED COBALTADITHIOLENE COMPLEX

Electrochemical investigations concerning the reduction of an alkylide ne adduct of a cobaltadithiolene complex are described. [(Cp)Co{S2C2(C OOMe)(2)}{C(COOMe)(2)}] (Cp = eta(5)-C5H5) exists as an equilibrium mi xture of alkylidene-bridged (2) and ylide, forms (3) in solution. Both . isomers are reducible by one electron, but the radical anion of the bridged form (2-) undergoes rapid and irreversible isomerization to th e ylide form anion (3-). Conventional cyclic voltammetry (CV), thin-la yer CV, optically transparent thin-layer electrode (OTTLE), and differ ential pulse polarography (DPP) have been used to establish these mech anisms. In the reaction with trimethyl phosphite, an X-ray structure a nalysis and CV have also been used to prove the existence of the ylide structure.